1. Field of the Invention
The present invention relates to a water-in oil emulsion comprising an oligomer or a polymer derived from a polyolefin, and its use as a cosmetic, dermatological or pharmaceutical composition. It may be intended in particular for skin, lip and nail care, for make-up removal and/or for cleansing the skin, and/or as make-up for the skin and/or the lips. It may be used more particularly for the treatment of dry skin and/or lips and/or sensitive skin.
2. Discussion of the Background
In the cosmetic and dermatological fields, it is common to use creams consisting of a water-in-oil (W/O) emulsion comprising aqueous globules dispersed in an oily phase. These emulsions comprise a continuous oily phase and therefore make it possible to form, at the surface of the skin, a lipid film which prevents transepidermal water loss, protects the skin from external attacks and can also increase the persistence of sunscreen. Water-in-oil emulsions also make it possible to protect and to carry hydrophilic active agents sensitive to oxidation. These emulsions are particularly appropriate for the care and the repair of dry and dehydrated skin to which they provide comfort and protection by virtue of the lipid barrier which they form on the skin.
However, despite their great efficacy, W/O emulsions constitute a minority of the galenic forms used in the cosmetic field because they pose two major problems. First of all, these emulsions have the disadvantage of generally lacking cosmetic pleasantness, that is to say, they are greasy, heavy, sticky and lack a fresh sensation because of the oily outer phase. They are generally difficult to apply to the skin, they penetrate with difficulty and they leave a shiny and often sticky residual film on the skin.
Moreover, W/O emulsions exhibit problems of stability, in particular when the aqueous phase is in a large quantity or when the emulsion is fluid (consistency of a milk rather than of a cream). The drops of aqueous phase have, in this case, the tendency to aggregate and to form lumps which are visible under a microscope. This aggregation is detrimental to the stability of the emulsions; it promotes, on the one hand, creaming or sedimentation of the fluid systems, and, on the other hand, the coalescence of the drops, leading to the appearance of water domains, that is to say drops of aqueous phase greater than 50 microns in size. It is often necessary, to stabilize these emulsions, to use a high level of emulsifier and/or to introduce a certain quantity of consistency factors such as waxes. However, these ingredients contribute towards increasing the cosmetic defects (gummy and greasy effect) of the W/O emulsions resulting in compositions being obtained which are often compact and heavy. Moreover, in the presence of these consistency factors, it is difficult to obtain fluid emulsions, because these factors thicken the emulsions. Furthermore, if the content of emulsifier in these emulsions is greatly increased to remedy their instability, the emulsions obtained may prove irritant towards certain types of skin, in particular sensitive skin.
Thus, a large number of water-in-oil emulsions exist which are stabilized by various surfactants, in particular alkylated derivatives of polyglycerol, alkylated polyethylene glycols, alkylated derivatives of sorbitan, metal salts of fatty acids and silicone surfactants. However, in the majority of the emulsions stabilized by hydrocarbon-containing surfactants, the content of aqueous phase should remain less than 80% by weight and the level of surfactant should be relatively high, so as to be able to produce an emulsion with acceptable stability. Moreover, it is generally necessary to increase the viscosity of the oily phase by adding waxes (see for example DE 3 430 256), oily gelling agents (see for example EP 0 795 321) or modified clays (see for example EP 0 331 833) in order to improve the stability of the emulsions. The products resulting therefrom often lack a sensation of freshness and lightness.
In addition, silicone surfactants can improve the cosmetic properties of water-in-oil emulsions. However, the sense of feel remains characteristic of silicones, and silicone oils generally have to be the predominant constituents of the oily phase. Moreover, generally, it is necessary to couple these surfactants with at least one other surfactant, most often a hydrocarbon containing surfactant, in order to make the stability of the emulsion perfect. A need therefore remains for a stable water-in-oil emulsion which does not exhibit the disadvantages encountered of conventional and known water-in-oil emulsions, in particular for an emulsion with a light and fresh feel, containing no silicone surfactant and which may be fluid and/or which may have a high content of aqueous phase and which exhibits good stability, even in the absence of factors for which enhance the consistency of the oily phase, in particular even in the absence of waxes.